This invention relates to a thermodynamic system for thermal treatment and to a machine comprising the system, for making liquid and semi-liquid products.
In the sector of machines for making liquid and semi-liquid products such as ice creams, cake and pastry fillings and the like, it is standard practice to thermally treat a product (by heating and/or cooling) in order to make a predetermined recipe.
Known in the prior art is a plurality of thermal systems of thermodynamic type which allow a product to be thermally treated in a container in order to modify its food qualities.
Most thermodynamic systems for cooling are based on the inverse Carnot cycle (“saturated vapor compression”): these systems allow a container to be cooled by means of a thermodynamic circuit operating on a heat exchanger fluid and comprising a pair of exchangers (evaporator and condenser), a compressor and a laminar flow element, with the heat exchanger fluid flowing through all of them.
FIG. 2 illustrates a thermal treatment system of known type based on the inverse Carnot cycle and comprising a suction line heat exchanger.
Generally speaking, the refrigerating cycle with the liquid-suction exchanger is particularly efficient.
Further, a thermodynamic system with a liquid-suction exchanger allows undercooling the refrigerant liquid flowing out of the condenser in order to prevent the formation of vapor bubbles (or “flash gas”) in the liquid upstream of the expansion element (which would cause noise and rapid wear of the system).
A thermodynamic system with a liquid-suction exchanger also allows overheating any residual liquid (causing it to evaporate completely) inside the suction line upstream of the compressor which would otherwise lead to rapid wear of the compressor components if it were to find its way into the compressor.
Evident from the above are the advantages of a thermodynamic system with a liquid-suction exchanger. This type of system is thus particularly suitable for machines for making liquid or semi-liquid products, which must be highly reliable and low noise in operation.
A growing need felt by machine manufacturers is that of having a thermodynamic system adapted to thermally treat very small quantities of ingredients (for example, single serve machines) where the amounts of heat exchanged through the heat exchangers are particularly small.
In particular, in the ice cream sector, experimental studies conducted by the applicant have shown that existing thermodynamic systems are unable to operate efficiently and stably when the amounts of heat that need to be exchanged are very small.
It should also be stressed that in single serve ice cream machines, ice cream production times are particularly short (in the order of a few minutes).
Ice cream processing requires a particularly stable thermal system operating according to predetermined theoretical mixture cooling profiles, failing which the end product is inevitably poorer in quality.
In this context, in order to make an ice cream of optimal quality, it is essential to control very precisely the temperature of the basic mixture being processed.
Consequently, a need which is particularly strongly felt by machine manufacturers is that of having a refrigeration system whose operation is particularly stable and which is easy to control, even for very small heat requirements, that is to say, for small volumes of basic mixture.